Various corrosive gases such as a hydrogen sulfide gas are contained in the atmosphere in a living environment. Even with low concentrations, the corrosive gases corrode electronic equipment or the like and accelerate its deterioration. Monitoring the corrosive gases in an environment where the electronic equipment is placed is effective in grasping the influence of the corrosive gases on the electronic equipment.
A QCM sensor is one of corrosion sensors for monitoring corrosive gases. The QCM sensor includes a quartz plate provided with electrodes on both principal surfaces, and is configured to oscillate the quartz plate at a natural oscillation frequency by applying a predetermined voltage to the electrodes under actual use conditions.
The above-described natural oscillation frequency decreases along with an increase in mass of the electrodes of the QCM sensor due to corrosion by the corrosive gases. Thus, the approximate amount of the corrosive gases contained in the environment may be monitored by measuring the amount of decrease in the natural oscillation frequency.
Also, an improvement in sensitivity of the QCM sensor enables the QCM sensor to measure the influence of a low concentration of corrosive gases at a short time.
Patent Document 1: Japanese Laid-open Patent Publication No. 05-296907
Patent Document 2: Japanese Laid-open Patent Publication No. 08-228123
Patent Document 3: Japanese Examined Laid-open Patent Publication No. Hei 06-24301